John V Jackson wrote:
<snip>
> snagging on things would have been paid for, but most af all, they will
> have given DRAG.
>
> However, drag is exactly what you want when you are falling out of a tree.
> On its own, it can save your life. Animals of about cat-size or smaller,
> if they have sufficient drag, and if they land on their feet on normal
> ground, can usually survive a fall from any height, ie at terminal
> velocity. For them in particular, fluffiness of some kind is very likely
> indeed to confer evolutionary advantage. (Consider various tree-top living
> monkeys such as colobos (>cats, I know) etc, and maybe some of the smaller
> south American ones, and compare with the more ground-dwelling macaques.
> Also compare furry-tailed squirrels with bare-tailed rats, and small-tailed
> prairy dogs and chipmunks.)
This is definitely true, though perhaps overstated. Small animals are less
hurt by falls than large animals primarily because of mass and the square-cube
law. Feathers-as-drag would be a help to a fall-prone arboreal animal, but
OTOH it could gain similar benefits at less expense just by becoming less prone
to falling.
> There is an insulation paradox for evolving from cold to warm bloodied:
> Warm bloods need it, but cold bloods cant's have it. With birds, I suggest
> that the drive towards feathers for parachuting/gliding/flying made warm
> bloodedness increasingly feasible in a parallel way. Notice Squamosia or
> whatever it was called had feathers/scales growing out of the top of its
> back, in such a way so as not to interfere with sunbathing in sideways
> sunshine. And as for mammals? Well, how about prickles?
>
To my (admittedly amateur's) eyes, this doesn't make much sense. I grant that
insulation is necessary for warmbloods and a very bad idea for coldbloods --
_if_ you define "warmblood" as 100% endothermic, and "coldblood" as 100%
ectothermic, and don't permit any intermediate stages. But if you allow
intermediate stages, "partial endotherms" as it were, doesn't it make sense
that endothermy and insulation would evolve in parallel, with insulation just
one of several traits required to make a viable endothermic animal?.
-- Jon W.